Oligodendrocytes and their precursors require phosphatidylinositol 3-kinase signaling for survival

Development ◽  
1996 ◽  
Vol 122 (8) ◽  
pp. 2529-2537
Author(s):  
G.S. Vemuri ◽  
F.A. McMorris
Keyword(s):  
Cell Death ◽  
Enzyme Activity ◽  
Growth Factors ◽  
Growth Factor ◽  
Cell Survival ◽  
Nuclear Dna ◽  
Apoptotic Cell ◽  
Terminal Deoxynucleotidyl Transferase ◽  
Phosphatidylinositol 3 Kinase ◽  
Phosphatidylinositol 3

Signal transduction in response to several growth factors that regulate oligodendrocyte development and survival involves the activation of phosphatidylinositol 3-kinase, which we detect in oligodendrocytes and their precursors. To investigate the role of this enzyme activity, we analyzed cell survival in cultures of oligodendrocytes treated with wortmannin or LY294002, two potent inhibitors of phosphatidylinositol 3-kinase. Cell survival was inhibited by 60–70% in these cultures within 24 hours, as quantitated by a tetrazolium staining assay for viable cells and by measurement of DNA content. Similar results were obtained with oligodendrocyte precursor cells. Nuclei of the dying cells contained fragmented DNA, as revealed by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling assays, indicating that the cells were dying by apoptosis. Moreover, a significant increase in the number of cells with fragmented nuclear DNA was detected as early as 4 hours, well before any significant differences could be detected in glucose transport or cell viability. Exogenous addition of insulin-like growth factor-I, neurotrophin-3, platelet-derived growth factor, basic fibroblast growth factor, ciliary neurotrophic factor, N-acetyl cysteine, vitamin C, vitamin E, progesterone or serum did not prevent cell death in the presence of wortmannin or LY294002. These findings indicate that survival of oligodendrocytes and their precursors depends on a phosphatidylinositol 3-kinase mediated signaling pathway. Inhibition of this critical enzyme activity induces apoptotic cell death, even in the presence of exogenous growth factors or serum.

scholarly journals Cytokine Stimulation Promotes Glucose Uptake via Phosphatidylinositol-3 Kinase/Akt Regulation of Glut1 Activity and Trafficking

2007 ◽  
Vol 18 (4) ◽  
pp. 1437-1446 ◽  
Author(s):  
Heather L. Wieman ◽  
Jessica A. Wofford ◽  
Jeffrey C. Rathmell
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Glucose Uptake ◽  
Glucose Transporter ◽  
Glycogen Synthase ◽  
Mammalian Target Of Rapamycin ◽  
Phosphatidylinositol 3 Kinase ◽  
Akt Activation ◽  
Cytokine Stimulation ◽  
Phosphatidylinositol 3

Cells require growth factors to support glucose metabolism for survival and growth. It is unclear, however, how noninsulin growth factors may regulate glucose uptake and glucose transporters. We show that the hematopoietic growth factor interleukin (IL)3, maintained the glucose transporter Glut1 on the cell surface and promoted Rab11a-dependent recycling of intracellular Glut1. IL3 required phosphatidylinositol-3 kinase activity to regulate Glut1 trafficking, and activated Akt was sufficient to maintain glucose uptake and surface Glut1 in the absence of IL3. To determine how Akt may regulate Glut1, we analyzed the role of Akt activation of mammalian target of rapamycin (mTOR)/regulatory associated protein of mTOR (RAPTOR) and inhibition of glycogen synthase kinase (GSK)3. Although Akt did not require mTOR/RAPTOR to maintain surface Glut1 levels, inhibition of mTOR/RAPTOR by rapamycin greatly diminished glucose uptake, suggesting Akt-stimulated mTOR/RAPTOR may promote Glut1 transporter activity. In contrast, inhibition of GSK3 did not affect Glut1 internalization but nevertheless maintained surface Glut1 levels in IL3-deprived cells, possibly via enhanced recycling of internalized Glut1. In addition, Akt attenuated Glut1 internalization through a GSK3-independent mechanism. These data demonstrate that intracellular trafficking of Glut1 is a regulated component of growth factor-stimulated glucose uptake and that Akt can promote Glut1 activity and recycling as well as prevent Glut1 internalization.

Insulin and insulin-like growth factor-1 promote mast cell survival via activation of the phosphatidylinositol-3-kinase pathway

2006 ◽  
Vol 34 (11) ◽  
pp. 1532-1541 ◽  
Author(s):  
Eva Lessmann ◽  
Gordon Grochowy ◽  
Lars Weingarten ◽  
Torsten Giesemann ◽  
Klaus Aktories ◽  
...  
Keyword(s):  
Mast Cell ◽  
Growth Factor ◽  
Cell Survival ◽  
Insulin Like Growth Factor ◽  
Phosphatidylinositol 3 Kinase ◽  
Kinase Pathway ◽  
Phosphatidylinositol 3

scholarly journals Phosphatidylinositol 3-kinase, protein kinase B and ribosomal S6 kinases in the stimulation of thyroid epithelial cell proliferation by cAMP and growth factors in the presence of insulin

2000 ◽  
Vol 348 (2) ◽  
pp. 351-358 ◽  
Author(s):  
Katia COULONVAL ◽  
Fabrice VANDEPUT ◽  
Rob C. STEIN ◽  
Sara C. KOZMA ◽  
Françoise LAMY ◽  
...  
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Protein Kinase ◽  
Dna Synthesis ◽  
Protein Kinase B ◽  
Phosphatidylinositol 3 Kinase ◽  
S6 Kinase ◽  
P70 S6 Kinase ◽  
Stimulation Of ◽  
Phosphatidylinositol 3

The proliferation of most normal cells depends on the co-operation of several growth factors and hormones, each with a specific role, but the key events involved in the action of each necessary stimulant remain largely uncharacterized. In the present study, the pathways involved in the mechanism(s) of co-operation have been investigated in primary cultures of dog thyroid epithelial cells. In this physiologically relevant system, thyroid stimulating hormone (TSH) acting through cAMP, epidermal growth factor (EGF) and phorbol esters (such as PMA) induce DNA synthesis. Their effect requires stimulation of the insulin-like growth factor-1 (IGF-1) receptor by either IGF-1 or insulin, which are not themselves mitogenic agents. In contrast, hepatocyte growth factor (HGF) is itself fully mitogenic. The results of the study demonstrate that cAMP, EGF, HGF and PMA stimulate p70 ribosomal S6 kinase (p70 S6 kinase). However, insulin/IGF-1 also stimulate p70 S6 kinase. Thus stimulation of p70 S6 kinase might be necessary, but is certainly not sufficient, for the induction of DNA synthesis and is not specific for any stimulated pathway. In contrast, phosphatidylinositol 3-kinase (PI 3-kinase) and protein kinase B (PKB) activation by insulin and HGF is strong and sustained, whereas it is weak and transient with EGF and absent in the presence of TSH or PMA. These findings suggest that: (i) stimulation of PI 3-kinases and/or PKB is not involved in the cAMP-dependent pathways leading to thyrocyte proliferation, or in the action of PMA, (ii) the stimulation of the PI 3-kinase/PKB pathway may account for the permissive action of insulin/IGF-1 in the proliferation of these cells, and (iii) the stimulation of this pathway by HGF may explain why this agent does not require insulin or IGF-1 for its mitogenic action.

Lithium activates the Wnt and phosphatidylinositol 3-kinase Akt signaling pathways to promote cell survival in the absence of soluble survival factors

2005 ◽  
Vol 288 (4) ◽  
pp. F703-F713 ◽  
Author(s):  
Diviya Sinha ◽  
Zhiyong Wang ◽  
Kathleen L. Ruchalski ◽  
Jerrold S. Levine ◽  
Selvi Krishnan ◽  
...  
Keyword(s):  
Growth Factor ◽  
Protective Effect ◽  
Wnt Signaling ◽  
Cell Survival ◽  
Conditioned Medium ◽  
Wnt Pathway ◽  
Phosphatidylinositol 3 Kinase ◽  
Apoptotic Pathway ◽  
Akt Phosphorylation ◽  
Phosphatidylinositol 3

Mouse proximal tubular cells (BUMPT), when cultured in the absence of growth factors, activate a default apoptotic pathway. Although Wnt signaling antagonizes the effect of proapoptotic triggers, its role in regulating the default pathway of apoptosis is less well defined. The present study examines the hypothesis that lithium (Li+) and (2′Z,3′E)-6-bromoindirubin-3′-oxime (BIO), two glycogen synthase kinase-3β (GSK3β) inhibitors, promote survival of growth factor-deprived renal epithelial cells by activating the Wnt pathway. These studies demonstrate that Li+ and BIO activate Wnt signaling as indicated by the following changes: phosphorylation (inhibition) of GSK3β; decreased phosphorylation of β-catenin (a GSK3β substrate); nuclear translocation of β-catenin; specific transcriptional activation of Tcf/catenin-responsive pTopflash constructs; and an increase in the expression of cyclin D1 (indicative of a promitogenic cell response). In addition, Li+ or BIO significantly increases the phosphorylation (activation) of Akt, an anti-apoptotic protein, and inhibits apoptosis (decreases both annexin-V staining and caspase-3 activation), during serum deprivation. Inhibition of phosphatidylinositol 3-kinase (responsible for Akt activation) either by wortmanin or LY-294002 prevented Li+- or BIO-induced Akt phosphorylation and reduces cell survival without altering the phosphorylation state of GSK3β. Li+ or BIO also increases the expression of insulin-like growth factor-II (IGF-II), a potent proliferative signaling protein. Li+ or BIO-free conditioned medium harvested from Li+- or BIO-exposed cells also induced Akt phosphorylation, mimicking the protective effect of the two GSK3β inhibitors on serum-starved cells. Furthermore, the effect of conditioned medium on Akt phosphorylation could be inhibited by either LY-294002 or IGF-binding protein. BIO, a specific GSK3β inhibitor, replicated the protective effect of Li+ on cell viability, suggesting that GSK3β activation is important for initiating the apoptotic pathway. Taken together, these data suggest that Li+ or BIO promotes renal epithelial cell survival by inhibiting apoptosis through GSK3β-dependent activation of the Wnt pathway and subsequent release of IGF-II. Extracellular IGF-II serves as an autocrine survival factor that is responsible, in part, for activating the anti-apoptotic phosphatidylinositol-3-kinase-Akt pathway during serum deprivation.

scholarly journals Apoptosis Suppression by Raf-1 and MEK1 Requires MEK- and Phosphatidylinositol 3-Kinase-Dependent Signals

2001 ◽  
Vol 21 (7) ◽  
pp. 2324-2336 ◽  
Author(s):  
Alexander von Gise ◽  
Petra Lorenz ◽  
Claudia Wellbrock ◽  
Brian Hemmings ◽  
Friederike Berberich-Siebelt ◽  
...  
Keyword(s):  
Cell Death ◽  
Cell Survival ◽  
Cell Line ◽  
Active Form ◽  
Dominant Negative ◽  
Phosphatidylinositol 3 Kinase ◽  
Interleukin 3 ◽  
Survival Signaling ◽  
Phosphatidylinositol 3 ◽  
Constitutively Active

ABSTRACT Two Ras effector pathways leading to the activation of Raf-1 and phosphatidylinositol 3-kinase (PI3K) have been implicated in the survival signaling by the interleukin 3 (IL-3) receptor. Analysis of apoptosis suppression by Raf-1 demonstrated the requirement for mitochondrial translocation of the kinase in this process. This could be achieved either by overexpression of the antiapoptotic protein Bcl-2 or by targeting Raf-1 to the mitochondria via fusion to the mitochondrial protein Mas p70. Mitochondrially active Raf-1 is unable to activate extracellular signal-related kinase 1 (ERK1) and ERK2 but suppresses cell death by inactivating the proapoptotic Bcl-2 family member BAD. However, genetic and biochemical data also have suggested a role for the Raf-1 effector module MEK-ERK in apoptosis suppression. We thus tested for MEK requirement in cell survival signaling using the interleukin 3 (IL-3)-dependent cell line 32D. MEK is essential for survival and growth in the presence of IL-3. Upon growth factor withdrawal the expression of constitutively active MEK1 mutants significantly delays the onset of apoptosis, whereas the presence of a dominant negative mutant accelerates cell death. Survival signaling by MEK most likely results from the activation of ERKs since expression of a constitutively active form of ERK2 was as effective in protecting NIH 3T3 fibroblasts against doxorubicin-induced cell death as oncogenic MEK. The survival effect of activated MEK in 32D cells is achieved by both MEK- and PI3K-dependent mechanisms and results in the activation of PI3K and in the phosphorylation of AKT. MEK and PI3K dependence is also observed in 32D cells protected from apoptosis by oncogenic Raf-1. Additionally, we also could extend these findings to the IL-3-dependent pro-B-cell line BaF3, suggesting that recruitment of MEK is a common mechanism for survival signaling by activated Raf. Requirement for the PI3K effector AKT in this process is further demonstrated by the inhibitory effect of a dominant negative AKT mutant on Raf-1-induced cell survival. Moreover, a constitutively active form of AKT synergizes with Raf-1 in apoptosis suppression. In summary these data strongly suggest a Raf effector pathway for cell survival that is mediated by MEK and AKT.

scholarly journals R-Ras promotes apoptosis caused by growth factor deprivation via a Bcl-2 suppressible mechanism.

1995 ◽  
Vol 129 (4) ◽  
pp. 1103-1114 ◽  
Author(s):  
H G Wang ◽  
J A Millan ◽  
A D Cox ◽  
C J Der ◽  
U R Rapp ◽  
...  
Keyword(s):  
Cell Death ◽  
Growth Factor ◽  
Cell Survival ◽  
Apoptotic Cell ◽  
Small Gtpases ◽  
Ras Protein ◽  
Cell Death Pathway ◽  
Promote Cell Survival ◽  
Expression Plasmids

The Bcl-2 protein is an important regulator of programmed cell death, but the biochemical mechanism by which this protein prevents apoptosis remains enigmatic. Recently, Bcl-2 has been reported to physically interact with a member of the Ras superfamily of small GTPases, p23-R-Ras. To examine the functional significance of R-Ras for regulation of cell death pathways, the IL-3-dependent cells 32D.3 and FL5.12 were stably transfected with expression plasmids encoding an activated form (38 Glycine-->Valine) of R-Ras protein. R-Ras(38V)-producing 32D.3 and FL5.12 cells experienced increased rates of apoptotic cell death relative to control transfected cells when deprived of IL-3. Analysis of several independent clones of transfected 32D.3 cells revealed a correlation between higher levels of R-Ras protein and faster rates of cell death upon withdrawal of IL-3 from cultures. 32D.3 cells cotransfected with R-Ras(38V) and Bcl-2 exhibited prolonged cell survival in the absence of IL-3, equivalent to 32D.3 cells transfected with Bcl-2 expression plasmids alone. R-Ras(38V) also increased rates of cell death in serum-deprived NIH-3T3 cells, and Bcl-2 again abrogated most of this effect. The ratio of GTP and GDP bound to R-Ras(38V) was not significantly different in control 32D.3 cells vs those that overexpressed Bcl-2, indicating that Bcl-2 does not abrogate R-Ras-mediated effects on cell death by altering R-Ras GDP/GTP regulation. Moreover, purified Bcl-2 protein had no effect on the GTPase activity of recombinant wild-type R-Ras in vitro. When expressed in Sf9 cells using recombinant baculoviruses, R-Ras(38V) bound to and induced activation of Raf-1 kinase irrespective of whether Bcl-2 was coproduced in these cells, suggesting that Bcl-2 does not nullify R-Ras effects by interfering with R-Ras-mediated activation of Raf-1 kinase. Taken together, these findings suggest that R-Ras enhances the activity of a cell death pathway in growth factor-deprived cells and imply that Bcl-2 acts downstream of R-Ras to promote cell survival.

scholarly journals Characterization of the intracellular signalling pathways that underlie growth-factor-stimulated glucose transport in Xenopus oocytes: evidence for ras- and rho-dependent pathways of phosphatidylinositol 3-kinase activation

1997 ◽  
Vol 325 (3) ◽  
pp. 637-643 ◽  
Author(s):  
Fiona J. THOMSON ◽  
Thomas J. JESS ◽  
Colin MOYES ◽  
Robin PLEVIN ◽  
Gwyn W. GOULD
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
G Protein ◽  
Glucose Transport ◽  
Dominant Negative ◽  
Signalling Pathways ◽  
Phosphatidylinositol 3 Kinase ◽  
Igf I ◽  
G Protein Coupled ◽  
Phosphatidylinositol 3

The stimulation of glucose transport is one of the early cellular responses to growth factors and is essential for cell proliferation, yet the molecular processes that underlie this response are poorly defined. The aim of this study was to characterize the role of the low-molecular-mass G-proteins, Ras and Rho, and their downstream targets, Raf protein kinase and phosphatidylinositol 3-kinase, in the regulation of glucose transport in Xenopusoocytes by two distinct growth-factor receptors: the insulin-like growth factor I (IGF-I) tyrosine kinase receptor and the heterotrimeric G-protein-coupled lysophosphatidic acid (LPA) receptor. Microinjection of a neutralizing anti-Ras antibody partially blocked IGF-I-stimulated deoxyglucose uptake but was without effect on LPA-stimulated deoxyglucose uptake. In contrast, microinjection of the C3 coenzyme of botulinum toxin, which selectively ADP-ribosylates and inactivates Rho, inhibited LPA-stimulated, but not IGF-I-stimulated, deoxyglucose uptake. Similarly, LPA- but not IGF-I-stimulated deoxyglucose uptake was attenuated in oocytes expressing a dominant negative rhoconstruct. Cells expressing a dominant negative mutant of Raf protein kinase exhibited markedly reduced sensitivity to both LPA and IGF-I, consistent with a role for endogenous Raf in glucose uptake by both growth factors. Furthermore, expression of a constitutively activated form of raf-1 resulted in a growth-factor-independent increase in deoxyglucose uptake. Measurements of phosphatidylinositol 3-kinase activity in microinjected cells support the hypothesis that the IGF-I receptor stimulates glucose transport by a Ras-dependent activation of phosphatidylinositol 3-kinase, whereas the G-protein-coupled LPA receptor controls this response by a pathway that involves Rho-dependent activation of a distinct phosphatidylinositol 3-kinase. Thus we provide evidence for clear differences in the signalling pathways that control glucose transport by G-protein-coupled and tyrosine kinase growth-factor receptors. Furthermore this is the first demonstration that active Rho is involved in the signalling pathways that regulate glucose uptake in response to some growth factors.

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